The cryogenic separation of mixtures such as air to produce oxygen and/or nitrogen is a well established industrial process. Liquid and vapor are passed in countercurrent contact through one or more columns and the difference in vapor pressure between the oxygen and nitrogen causes nitrogen to concentrate in the vapor and oxygen to concentrate in the liquid. The lower the pressure is in the separation column, the easier is the separation into oxygen and nitrogen due to vapor pressure differential. Accordingly, the final separation into product oxygen and/or nitrogen is generally carried out at a relatively low pressure, usually just a few pounds per square inch (psi) above atmospheric pressure.
Often the product oxygen and/or nitrogen is desired at an elevated pressure. In such situations, the product is compressed to the desired pressure in a compressor. This compression is costly in terms of energy costs as well as capital costs for the product compressors.
Accordingly, it is an object of this invention to provide an improved cryogenic rectification system for the production of oxygen and/or nitrogen.
It is a further object of this invention to provide an improved cryogenic rectification system for the production of oxygen and/or nitrogen wherein oxygen and/or nitrogen may be produced at elevated pressure thereby eliminating or reducing the need for product gas compression.